1. Field of the Invention
The present invention relates to a roller type test stand for motor vehicles and/or wheel/tire combinations. More particularly, the present inventions relations to a roller type test stand where bearings, lubrication devices and measuring equipment are prevented from introducing error into the test results.
2. Description of the Related Art
In testing vehicle dynamics parameters and exhaust emissions of motor vehicles driven by internal combustion engines, roller or drum type test stands are used that allow various driving conditions to be simulated. For example, in performing tests on braking functions, exhaust emissions, or the like, the vehicle to be tested is fixed in the correct position in the roller type test stand. Either both wheels of one axle or both wheels of several axles standing on the vertex region of respective pairs of running rollers, depending on the design of the test stand. The pairs of running rollers are coupled to driving and deceleration machines that are connected to measuring elements and measuring apparatuses for detecting the torques or tensile forces that occur under various test conditions.
German reference DE 199 00 620 A1 discloses a roller type test stand for motor vehicles in which both running rollers are driven directly in synchrony via a common shaft using an electric motor arranged centrally between the running rollers. The stator housing of this motor is swing mounted in a supporting frame and is supported on the supporting frame by a measuring apparatus designed as a dynamometer.
The stator housing and the motor rotor mounted on the housing designed as the aforementioned shaft are swing mounted on the supporting frame by means of leaf-spring elements or sliding bearings. The leaf spring elements present a small resistance to the twisting movement of the stator housing. The shaft is mounted in the swing mounting by means of sliding bearings.
The bearing shells of these sliding bearings are constructed with pocket or groove like depressions to avoid premature wear of the sliding bearings of the shaft and of the sliding bearings of the swing mounting. The sliding bearings are supplied with a constant volume flow of pressurized oil.
The object of the present invention is to provide a roller type test stand that give more accurate measurements with a reduced outlay in terms of construction.
According to the invention, the object is achieved by a set of running rollers driven by a motor/transmission combination that is grouped together as a unit in a swing mounted frame arranged between the running rollers. The frame serves to absorb all the high or excessive forces that occur during operation. A shaft for supporting the running rollers is mounted on the frame within the swing mounting so as to avoid bearing losses. At least one measuring apparatus, by means of which all the forces that occur can be determined, is arranged on the swing mounted frame.
The roller type test stand configured in accord with the present invention provides for an even more accurate measurement, which takes into account all the forces and losses, e.g., frictional losses, that occur during a measurement. The invention has the advantage that there are no bearings subject to loads due to rotational speed arranged outside the swing mounting. As a result, no forces or losses, e.g., frictional losses, that are not recorded by the measuring apparatus occur. In other words, all of the forces or losses intended for recordation are measured.
In an embodiment of the present invention one or more drive motors are used in the motor/transmission combination. The use of a plurality of drive motors makes it possible to employ motors with a lower torque and thus also smaller dimensions, thereby making it possible to achieve a compact motor/transmission combination.
In a preferred embodiment of the present invention, the transmission is configured as a gear set which comprises, for example, spur toothed gearwheels or cylindrical gearwheels and is flanged directly to the drive motors. Alternatively, the transmission can also be configured as a belt or chain drive.
Further advantages are apparent in the choice of lubricant to be used for this roller type test stand. It is possible to dispense with expensive pressurized oil lubrication. Lubricant is supplied to the transmission and the bearings, for example, by means of a splash lubrication system integrated into the frame carrying the motor/transmission combination. The temperature of the lubricant can be controlled by means of air/oil coolers integrated into the frame of the motor/transmission combination. A lubrication device of this kind integrated into the drive or motor/transmission combination has the particular advantage that external disturbances that that can falsify the measurement are avoided. Such disturbances can be caused, for example, by a lubricant supply device arranged outside the roller type test stand and connected via supply lines to the drive and the bearings.
In a further embodiment of the present invention, the frame is constructed with housing type elements and receiving means for accommodating assemblies such as the abovementioned air/oil cooler or the drive motors.
In a still further embodiment of the present invention, the motor/transmission combination can be made switchable and/or exchangable in order to adapt the accuracy of monitoring and measurement to various categories of vehicles to be tested. Switching can be achieved, for example, by the use of a shiftable transmission and/or by turning individual drive motors on and off.
To cool the motor/transmission combination, one or more fans are arranged separate from the swing mounted motor/transmission combination for supplying the motor/transmission combination with cooling air in a contactless manner using cooling air supply nozzles or ducts. This arrangement has the advantage of avoiding the introduction of disturbances that would falsify the measurement because assemblies such as fans, that can cause a possible disturbance or possible measurement error, are outside the test stand components for measurement and are arranged without a direct connection to the test stand components for measurement, e.g., by means of hoses or cables.
In an alternative embodiment, the motor/transmission combination can be mounted on a housing swing mounted on the supporting frame, rather than the frame. It is also possible for this housing to be directly associated with only one component of the motor/transmission combination e.g, a transmission housing or a motor housing. All other components belonging to the motor/transmission combination may likewise be mounted on this housing, with the housing being swing mounted on the supporting frame.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.